Fiber-optic rotational device, optical system and method for imaging a sample

ABSTRACT

A device, system and method for transmitting electro-magnetic radiation between at least two separate fibers (as well as for imaging a sample) are provided. For example, a first optical fiber and a second optical fiber may be provided, such that the first and/or second fibers is/are rotatable. At least one first optical arrangement may also be included which communicates with at least one end of the first optical fiber and/or the second optical fiber. Further, at least one second arrangement may be included which is configured to control a position of the optical arrangement to align longitudinal axes of the first and the second optical fibers at least at the ends thereof. In addition, at least one third arrangement can be provided which is adapted to rotate the first and/or second optical fibers at a rate that is greater than 40 revolutions per second. It is also possible to include at least one fourth arrangement which can be adapted for connecting the first optical fiber and/or the second optical fiber to a catheter arrangement, such that the fourth arrangement includes a protector provided at least at one end thereof, and wherein the protector is automatically removed upon a connection of the first and/or second optical fiber to the catheter arrangement via the fourth arrangement.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present invention claims priority from U.S. patent application Ser.No. 60/624,282 filed on Nov. 2, 2004, the entire disclosure of whichincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to optical imaging, and more particularlyoptical rotary junction devices, optical imaging systems and methodswhich utilize the rotary junction device for imaging a biologicalsample.

BACKGROUND OF THE INVENTION

In vivo optical imaging of internal organs of a patient is commonlyperformed through a fiber-optic catheter. Many clinical areas such ascardiology, neurocardiology, interventional radiology andgastroenterology require a rotating optical catheter to generate r-φcross-sectional images. In addition, the rotating catheter may be pulledback along a longitudinal direction to obtain 3D images of the tissuevolume of interest.

SUMMARY OF THE INVENTION

According to the present invention, the device preferably includes arotary junction that provides a catheter with a mechanical actuation andoptical connectivity between the catheter and an optical imaging engine.The optical imaging engine can perform optical frequency domain imaging(“OFDI”) and optical coherence tomography, as described in U.S.Provisional Patent Appn. No. 60/514,769 filed Oct. 27, 2003 andInternational Patent Application No. PCT/US03/02349 filed on Jan. 24,2003, respectively.

Therefore, exemplary embodiments of an optical rotary junction device,and optical imaging systems and methods that use the rotary junctiondevice are provided for performing imaging of a biological sample. Therotary junction can be used to transmit light between a stationaryoptical fiber port and a rotating optical fiber port. The stationaryfiber port may be connected to an imaging engine, and the rotatingoptical fiber can be connected to a fiber-optic catheter optically aswell as mechanically to produce a rotating probe beam at the distal endof the catheter. The rotary junction can further include a translationstage to obtain 3-dimensional images of the biological sample. Theexemplary imaging system which can use the rotary junction may includeintravascular imaging, cardiovascular imaging, neurovascular imaging andgastrointestinal tract imaging.

Thus, according to the exemplary embodiment of the present invention,device, system and method for transmitting electro-magnetic radiationbetween at least two separate fibers (as well as for imaging a sample)are provided. For example, a first optical fiber and a second opticalfiber may be provided, such that the first and/or second fibers is/arerotatable. At least one first optical arrangement may also be includedwhich communicates with at least one end of the first optical fiberand/or the second optical fiber. Further, at least one secondarrangement may be included which is configured to control a position ofthe optical arrangement to align longitudinal axes of the first and thesecond optical fibers at least at the ends thereof. In addition, atleast one third arrangement can be provided which is adapted to rotatethe first and/or second optical fibers at a rate that is greater than 10revolutions per second. It is also possible to include at least onefurther arrangement which can be adapted for connecting the firstoptical fiber and/or the second optical fiber to a catheter arrangement,such that the further arrangement may include a protector provided atleast at one end thereof, and wherein the protector is automaticallyremoved upon a connection of the first and/or second optical fiber tothe catheter arrangement via the fourth arrangement.

A translating arrangement can also be include with the exemplary device,system and method. This translating device may be configured totranslate the first optical fiber, the second optical fiber and/or theat least one second arrangement approximately along at least one of thelongitudinal axes. The rate may be greater than 1 millimeter per second.The third arrangement may situate therein the first optical fiber and/orthe second optical fiber. The third arrangement (e.g., a DC motor or astepping motor) can include an encoder which is configured to track therate. In addition, a motor may be connected to the third arrangementwhich is adapted to rotate the third arrangement. Such motor may includean encoder which is configured to track the rate.

According to another exemplary embodiment of the present invention, thesecond arrangement may include first and the second collimating lenses.Further, a numerical product of a focal length of the first and/or thesecond collimating lenses and a numerical aperture of a respective atleast one of the first and second optical fibers can be betweenapproximately 100 μm to 1000 μm. An optical transmission efficiencybetween the first and the second optical fibers may be greater thanapproximately 80%. The said transmission efficiency can be maintainedwith better than 1% accuracy during one full rotation of the secondfiber. The device may also have a back reflection of less than about −55dB.

In still another exemplary embodiment of the present invention, at leastone fourth arrangement (e.g., a wavelength-swept laser) may provide atleast one first electro-magnetic radiation to a sample and at least onesecond electro-magnetic radiation to a reference. A frequency ofradiation provided by the at least one fourth arrangement can vary overtime. In addition, at least one sixth arrangement may be provided fordetecting an interference between at least one third radiationassociated with the first radiation and at least one fourth radiationassociated with the second radiation. The first and thirdelectro-magnetic radiations may be transmitted via the first and/orsecond optical fibers. The variation over time of the fourth arrangementmay have a characteristic repetition rate, and the first and/or secondoptical fibers may be rotated by the third arrangement at asubstantially uniform rotation speed which is substantially equal to thecharacteristic repetition rate of the fourth arrangement divided by aninteger number between 250 and 5000.

In addition, a fifth arrangement may be provided for receiving at leastone first electro-magnetic radiation from a sample and at least onesecond electro-magnetic radiation from a reference. At least onespectral separating unit can be included which separates spectrum of thefirst electro-magnetic radiation and/or the second electro-magneticradiation into frequency components. Further, at least one eighthdetection arrangement may be provided which includes a plurality ofdetectors, each detector being capable of detecting at least a portionof at least one of the frequency components. The first electro-magneticradiation may be transmitted via the first optical fiber and/or thesecond optical fiber. The fifth arrangement may have a characteristicreadout repetition rate, and the first and/or second optical fibers maybe rotated by the third arrangement at a substantially uniform rotationspeed which is substantially equal to the characteristic readoutrepetition rate of the fifth arrangement divided by an integer numberbetween 250 and 5000. The catheter arrangement may be adapted to beinserted into a coronary artery.

These and other objects, features and advantages of the presentinvention will become apparent upon reading the following detaileddescription of embodiments of the invention, when taken in conjunctionwith the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages of the invention will becomeapparent from the following detailed description taken in conjunctionwith the accompanying figures showing illustrative embodiments of theinvention, in which:

FIG. 1(a) is an enlarged illustration of conventional fiber-opticcollimators using aspherical lens;

FIG. 1(b) is an enlarged illustration of conventional fiber-opticcollimators using graded-index lens;

FIG. 1(c) is an enlarged illustration of conventional fiber-opticcollimators using a pair of lenses;

FIG. 2 is a side cut-away view of an exemplary embodiment of an opticalrotary junction according to the present invention which uses a pair offiber collimators;

FIG. 3 is an illustration of an exemplary embodiment of a rotaryjunction according to the present invention;

FIG. 4 is a side view of an exemplary embodiment of a fiber-opticcatheter for biomedical imaging according to the present invention;

FIG. 5 is a schematic diagram of an exemplary embodiment of an opticalsystem according to the present invention which is based on an opticalfrequency domain imaging (“OFDI”) technique;

FIG. 6 is exemplary images of a coronary artery in vitro obtained usingthe OFDI technique;

FIG. 7 is a schematic diagram of another exemplary embodiment of anoptical system according to the present invention which is based on aspectral-domain optical coherence tomography (“SD-OCT”); and

FIG. 8 is exemplary images of a coronary artery in vitro obtained usingthe SD-OCT technique.

Throughout the figures, the same reference numerals and characters,unless otherwise stated, are used to denote like features, elements,components or portions of the illustrated embodiments. Moreover, whilethe present invention will now be described in detail with reference tothe figures, it is done so in connection with the illustrativeembodiments.

DETAILED DESCRIPTION

A fiber-optic collimator is a conventional component that is used totransform light emitted from a tip of an optical fiber 10, a shown inFIGS. 1(a)-1(c), to a collimated beam 16 or to launch light from acollimated beam to an optical fiber. Typically, an aspherical lens 11 orgraded refractive-index (GRIN or SELFOC) lens 12 may be used (as shownin FIGS. 1(a) and 1(b)). A pair of collimators can be used to transmitan optical beam from one fiber 12 to the other fiber 20 with minimalinsertion loss and back reflection (as shown in FIG. 1(c)). Thisconventional arrangement has been widely utilized to fiberize anotherwise free-space optical component such as polarizer, filter, andisolator.

FIG. 2 depicts a side view of an exemplary embodiment of a rotaryjunction according to the present invention which uses a pair ofcollimators 12, 18. One of the collimating lenses 18 is attached to atubular structure 26. The distal end of the fiber 20 is inserted into aconnector ferrule 28 which is positioned inside a sleeve 34. A matchingconnector with a connector housing case 33 and ferrule 32 is inserted tothe sleeve 34. This exemplary arrangement facilitates an opticaltransmission between two fibers 20 and 30. The tubular structure 26 isconnected to a housing 39 via a bearing 36. The tubular structure 26 isalso connected to a rotational motor 37 through a belt or gear 38. Themotor 37 rotates the tubular structure 26 and thereby the collimator 18.The housing 39 is mounted to a translation stage 40 mounted on astationary rail 41 for pull back operation. The rotary junction providesoptical transmission between a non-rotating fiber 10 and a rotatingfiber 30 while permitting interchange of alternate fibers 30 at theconnector housing 33.

The optical fibers 10, 20, 30 are preferably single mode optical fibers,but may be a multimode fiber, polarization maintaining fiber, orphotonic crystal fiber. The fibers 10, 20 can be fused to the lenses 12,18, thus potentially dramatically reducing back-reflection andincreasing throughput. The collimating lenses 12, 18 may alternately beaspheric refractive lenses or axial gradient index lenses. The opticalsurfaces of the lenses 12, 18 may be antireflection coated at anoperating wavelength range of light. The wavelength range can be800+/−100 nm, 1000-1300 nm, 1600-1800 nm, as well as other ranges. Thefocal length of the lenses 12, 18 may be selected to provide a beamdiameter of 100 to 1000 μm. The overall throughput from the fiber 10 to30 may be greater than 70%, and the back reflection is less than −55 dB.The precision coaxial alignment of the two collimators can provideuniformity of the throughput and the back reflection that is better thanapproximately 1% over a full rotation. The tubular structure 26 may be ahollow motor shaft and the motor 37 is positioned coaxially to thetubular structure 26; in this case the belt or gear 38 is not needed.The polishing angle of the connectors 28, 32 is typically between 4 to10 degrees with respect to the surface normal to minimize backreflection. The connector housing 33 preferably provides snap-onconnection like the SC type and is equipped with a built-inend-protection gate. FIG. 3 depicts a more detailed illustration of anexemplary embodiment of the rotary junction according to the presentinvention.

FIG. 4 shows an illustration of an exemplary embodiment of a fiber-opticcatheter for biomedical imaging in vivo as well as in vitro according tothe present invention, For example, the optical fiber is inserted to ashaft 45, and to the distal end beam focusing optics such as a spacer50, lens 52, and prism 60 are attached to generate a focusing beam 62.The optical fiber is preferably a single mode fiber consisting of a core42, cladding 43 and jacket 44. The beam focusing optics 50, 52, 60 andthe shaft 45 are bonded together securely to facilitate the rotation ofthe probe beam 62 at uniform rotational speed. A protection sheath 48 isconnected to the housing 39 of the rotary junction so that it staysrelatively stationary within a sample 70, protecting the sample frombeing damaged by the rotating shaft and vice versa. The spacing 46between the shaft 45 and the sheath 48 may be filled with an indexmatching liquid. In some applications such as intravascular orgastrointestinal imaging, a balloon is utilized to precisely locate thecatheter at the center of the tubular organ and/or to temporarily blockthe blood flow.

FIG. 5 shows an exemplary embodiment of an optical frequency domainimaging (“OFDI”) system which can use the exemplary rotary junction andcatheter according to the present invention. For example, the lightsource may be a wavelength swept laser 80. The rotary junction 39 can beconnected to the sample arm of an interferometer comprising a 10/90coupler 82, attenuator 84, polarization controller 86, circulators 88,89, length matching fiber 90, collimating lens 92, reference mirror 94.The detection circuit can include a 50/50 coupler 96, polarizationcontroller 98, polarization beam splitters 100, 101, dual balancedreceivers 103, 104, electrical filters 106, 107, and data acquisitionboard 110. The data acquisition may be connected to a computer 112, andis in communication with a trigger circuit 114, a motor controller 94,and the translation stage 41, 42. The operating principle of OCT is wellknown in the art. In addition, to provide dual-balanced and polarizationdiverse detection, e.g., simultaneously, the polarization controller 98allows the birefringence of the two fiber paths from the coupler to bematched. Another polarization controller 86 in the reference arm may beadjusted to split the reference light with an equal ratio at eachpolarization beam splitter 101, 102. Corresponding polarization statesfollowing the splitters, labeled x or y, may be directed todual-balanced receivers 103, 104.

The exemplary embodiment of the system shown in FIG. 5 may be used toperform intravascular OFDI in human coronary arteries in vitro. Thereceiver signals after low-pass filtering may be digitized with asampling frequency of 10 MHz using a PC data acquisition board (e.g.,National Instruments, 6115). At a laser tuning rate of 36 kHz, thedetection sensitivity of the system was >105 dB for arbitrarypolarization states and the axial resolution can be 12 μm (e.g., inair). The rotary junction 39 may use a high-speed DC motor with aworking range of >100 revolutions per second. The catheter 30 mayutilize a gradient index lens and 90-degree prism at its distal end andprovided a transverse resolution of 25 μm. The rotary junction can bemounted on a motorized linear translation stage 41, 42 to performlongitudinal, 3D pull-back imaging. The relatively slow digitizationrate of the acquisition board which may be used in such experiments maypossible be insufficient to realize the full potential of the sweptsource for OFDI. At the maximum, 10 MHz sampling rate, both imagingspeed and axial image size may be compromised. To demonstrate imagingusing the OFDI system and catheter, the laser can be operated at areduced rate of 18 kHz and 512 samples were acquired per spectral sweepof the laser corresponding to an axial scanning depth of 2.2 mm (e.g.,in air). Images of a fixed human coronary artery 70 may be acquired at36 frames per second over the duration of 3 seconds as the catheter isrotated at 36 revolutions per second and pulled back longitudinally at aspeed of 7.2 mm/s. Section A of FIG. 6 shows a typical image comprising500 A-lines with 256 radial pixels which is acquired using the OFDIsystem of FIG. 5. An exemplary 3-dimensional image acquired for 3seconds is shown in FIG. 6B.

FIG. 7 shows an exemplary embodiment of a spectral-domain opticalcoherence tomography (SD-OCT”) system which can use the exemplary rotaryjunction and catheter according to the present invention. For example,the light source 120 includes a low coherence broadband source, pulsedbroadband source, or a wavelength varying source with repetitionsynchronized to the readout rate of a camera 122. The camera 122 employsa detector array 124 based on charge coupled devices or CMOS imager. Theinterference signal is directed to the detector array 124 using acollimator 126, diffraction element such as grating 128, and a focusinglens 130. The operating principle of OCT is well known in the art.

As an example, imaging of a human coronary artery 70 may be conductedusing a fiber-optic catheter. FIG. 8 shows the images which can beobtained using, e.g., the cw amplified spontaneous emission source (Aand B) and a swept source (C and D) at the same A-line acquisition rateof 18.94 kHz. The difference between images A and B and between C and Dmay be the rotational speed of the catheter, that can be 9.5 rps for Aand C, corresponding to 2000 A-lines per image, and 37.9 rps for B andD, corresponding to 500 A-lines per image.

The foregoing merely illustrates the principles of the invention.Various modifications and alterations to the described embodiments willbe apparent to those skilled in the art in view of the teachings herein.For example, the invention described herein is usable with the exemplarymethods, systems and apparatus described in U.S. Provisional PatentAppn. No. 60/514,769 filed Oct. 27, 2003, and International PatentApplication No. PCT/US03/02349 filed on Jan. 24, 2003, the disclosuresof which are incorporated by reference herein in their entireties.Indeed, the arrangements, systems and methods according to the exemplaryembodiments of the present invention can be used with any OCT system,OFDI system or other imaging systems. It will thus be appreciated thatthose skilled in the art will be able to devise numerous systems,arrangements and methods which, although not explicitly shown ordescribed herein, embody the principles of the invention and are thuswithin the spirit and scope of the present invention. In addition, allpublications, patents and patent applications referenced above areincorporated herein by reference in their entireties.

1. A device for transmitting electro-magnetic radiation between at leasttwo separate fibers, comprising: a first optical fiber and a secondoptical fiber, wherein at least one of the first optical fiber and thesecond optical fibers is rotatable; at least one first opticalarrangement communicating with at least one end of at least one of thefirst optical fiber and the second optical fiber; at least one secondarrangement configured to control a position of the at least one opticalarrangement to align longitudinal axes of the first optical fiber andthe second optical fiber at least at the ends thereof; and at least onethird arrangement adapted to rotate at least one of the first opticalfiber and the second optical fiber at a rate that is greater than 10revolutions per second.
 2. The device according to claim 1, furthercomprising at least one translating arrangement which is configured totranslate at least one of the first optical fiber, the second opticalfiber and the at least one second arrangement approximately along atleast one of the longitudinal axes.
 3. The device according to claim 2,wherein the rate of translation is greater than approximately 1millimeter per second.
 4. The device according to claim 1, wherein therate is greater than 30 revolutions per second.
 5. The device accordingto claim 1, wherein the third arrangement situates therein at least oneof the first optical fiber and the second optical fiber.
 6. The deviceaccording to claim 1, wherein the third arrangement includes an encoderwhich is configured to track the rate.
 7. The device according to claim5, wherein the third arrangement includes at least one of a DC motor ora stepping motor.
 8. The device according to claim 1, further comprisinga fourth arrangement adapted for connecting at least one of the firstand second optical fiber to a catheter arrangement, wherein the fourtharrangement includes a protector provided at least at one end thereof,and wherein the protector is automatically removed upon a connection ofthe at least one of the first and second optical fiber to the catheterarrangement.
 9. The device according to claim 1, wherein the at leastone second arrangement includes first and the second collimating lenses,and wherein a numerical product of a focal length of at least one of thefirst and the second collimating lenses and a numerical aperture of arespective at least one of the first and second optical fibers isbetween approximately 50 μm to 2000 μm.
 10. The device according toclaim 1, wherein an optical transmission efficiency between the firstand the second optical fibers is greater than approximately 80%.
 11. Thedevice according to claim 1, wherein the device has a back reflection ofless than about −55 dB.
 12. The device according to claim 1, furthercomprising: at least one fourth arrangement providing at least one firstelectro-magnetic radiation to a sample and at least one secondelectro-magnetic radiation to a reference, wherein a frequency ofradiation provided by the at least one fourth arrangement varies overtime; and at least one fifth arrangement detecting an interferencebetween at least one third radiation associated with the at least onefirst radiation and at least one fourth radiation associated with the atleast one second radiation, wherein the first and third electro-magneticradiations are transmitted via at least one of the first and secondoptical fibers.
 13. The device according to claim 12, wherein thevariation over time of the fourth arrangement has a characteristicrepetition rate, and wherein at least one of the first and secondoptical fibers is rotated by the at least one third arrangement at asubstantially uniform rotation speed which is substantially equal to thecharacteristic repetition rate of the fourth arrangement divided by aninteger number greater than
 250. 14. The device according to claim 1,further comprising: a fourth arrangement receiving at least one firstelectro-magnetic radiation from a sample and at least one secondelectro-magnetic radiation from a reference; at least one spectralseparating unit which separates spectrum of at least one of the firstelectro-magnetic radiation, the second electro-magnetic radiation and acombination of the first and second electro-magnetic radiation intofrequency components; and at least one fifth detection arrangementincluding a plurality of detectors, each detector capable of detectingat least a portion of at least one of the frequency components, whereinthe at least one first electro-magnetic radiation is transmitted via atleast one of the first optical fiber and the second optical fiber. 15.The device according to claim 14, wherein the fifth arrangement has acharacteristic readout repetition rate, and wherein at least one of thefirst and second optical fibers is rotated by the at least one thirdarrangement at a substantially uniform rotation speed which issubstantially equal to the characteristic readout repetition rate of thefifth arrangement divided by an integer number greater than
 250. 16. Thedevice according to claim 8, wherein the catheter arrangement is adaptedto be inserted into a coronary artery.
 17. The device according to claim1, wherein the second optical fiber includes a portion which is adaptedto expand a mode-field area of the electro-magnetic radiation.
 18. Adevice for transmitting electro-magnetic radiation between at least twoseparate fibers, comprising: a first optical fiber and a second opticalfiber, wherein at least one of the first optical fiber and the secondoptical fiber is rotatable; at least one first optical arrangementcommunicating with at least one end of at least one of the first opticalfiber and the second optical fiber; at least one second arrangementconfigured to control a position of the at least one optical arrangementto align longitudinal axes of the first optical fiber and the secondoptical fiber at least at the ends thereof; and at least one thirdarrangement adapted for connecting at least one of the first opticalfiber and the second optical fiber to a catheter arrangement, whereinthe at least one third arrangement includes a protector provided atleast at one end thereof, and wherein the protector is automaticallyremoved upon a connection of the at least one of the first and secondoptical fiber to the catheter arrangement via the at least one thirdarrangement.
 19. The device according to claim 18, further comprising atleast one translating arrangement which is configured to translate atleast one of the first optical fiber, the second optical fiber and theat least one second arrangement approximately along at least one of thelongitudinal axes.
 20. The device according to claim 18, furthercomprising at least one fourth arrangement adapted to rotate at leastone of the first and second optical fiber at a rate that is greater than10 revolutions per second.
 21. The device according to claim 20, whereinthe rate is greater than 30 revolutions per second.
 22. The deviceaccording to claim 18, wherein the fourth arrangement situates thereinat least one of the first and second optical fibers.
 23. The deviceaccording to claim 20, wherein the fourth arrangement includes anencoder which is configured to track the rate.
 24. The device accordingto claim 20, wherein the fourth arrangement includes at least one of aDC motor or a stepping motor.
 25. The device according to claim 18,wherein the at least one second arrangement includes first and thesecond collimating lenses, and wherein a numerical product of a focallength of at least one of the first and the second collimating lensesand a numerical aperture of a respective at least one of the first andsecond optical fibers is between approximately 50 μm to 2000 μm.
 26. Thedevice according to claim 18, wherein an optical transmission efficiencybetween the first and the second optical fibers is greater thanapproximately 80%.
 27. The device according to claim 18, wherein thedevice has a back reflection of less than about −55 dB.
 28. The deviceaccording to claim 18, further comprising: at least one fourtharrangement providing at least one first electro-magnetic radiation to asample and at least one second electro-magnetic radiation to areference, wherein a frequency of radiation provided by the at least onefourth arrangement varies over time; and at least one fifth arrangementdetecting an interference between at least one third radiationassociated with the at least one first radiation and at least one fourthradiation associated with the at least one second radiation, wherein thefirst and third electro-magnetic radiations are transmitted via at leastone of the first and second optical fibers.
 29. The device according toclaim 28, wherein the variation over time of the fourth arrangement hasa characteristic repetition rate, and wherein at least one of the firstand second optical fibers is rotated by the at least one thirdarrangement at a substantially uniform rotation speed which issubstantially equal to the characteristic repetition rate of the fiftharrangement divided by an integer number that is approximately greaterthan
 250. 30. The device according to claim 18, further comprising: afourth arrangement receiving at least one first electro-magneticradiation from a sample and at least one second electro-magneticradiation from a reference; at least one spectral separating unit whichseparates spectrum of at least one of the first electro-magneticradiation, the second electro-magnetic radiation and a combination ofthe first and second electro-magnetic radiation into frequencycomponents; and at least one fifth detection arrangement including aplurality of detectors, each detector capable of detecting at least aportion of at least one of the frequency components, wherein the atleast one first electro-magnetic radiation is transmitted via at leastone of the first optical fiber and the second optical fiber.
 31. Thedevice according to claim 30, wherein the fifth arrangement has acharacteristic readout repetition rate, and wherein at least one of thefirst and second optical fibers is rotated by the at least one thirdarrangement at a substantially uniform rotation speed which issubstantially equal to the characteristic readout repetition rate of thefifth arrangement divided by an integer number greater than about 250.32. The device according to claim 31, wherein the catheter arrangementis adapted to be inserted into a coronary artery.
 33. The deviceaccording to claim 18, wherein the second optical fiber includes aportion which is adapted to expand a mode-field area of theelectro-magnetic radiation.
 34. A system for imaging a sample,comprising: a source generating electro-magnetic radiation; a firstoptical fiber and a second optical fiber receiving at least one signalassociated with the electro-magnetic radiation, wherein at least one ofthe first and second fibers is rotatable; at least one first opticalarrangement communicating with at least one end of at least one of thefirst optical fiber and the second optical fiber; at least one secondarrangement configured to control a position of the at least one opticalarrangement to align longitudinal axes of the first optical fiber andthe second optical fiber at least at the ends thereof; and at least onethird arrangement adapted to rotate at least one of the first opticalfiner and the second optical fiber at a rate that is greater than 40revolutions per second.
 35. A system for imaging a sample, comprising: asource generating electro-magnetic radiation; a first optical fiber anda second optical fiber receiving at least one signal associated with theelectro-magnetic radiation, wherein at least one of the first and secondfibers is rotatable; at least one first optical arrangementcommunicating with at least one end of at least one of the first opticalfiber and the second optical fiber; at least one second arrangementconfigured to control a position of the at least one optical arrangementto align longitudinal axes of the first and the second optical fibers atleast at the ends thereof; and at least one third arrangement adaptedfor connecting at least one of the first and second optical fiber to acatheter arrangement, wherein the at least third arrangement includes aprotector provided at least at one end thereof, and wherein theprotector is automatically removed upon a connection of the at least oneof the first optical fiber and the second optical fiber to the catheterarrangement via the at least one third arrangement.